Timber is often sawed into lumber soon after being cut. This freshly cut lumber typically has a water content of between 60% and 80% by weight. In order to use this lumber for construction it must usually be dried so as to have a water content of approximately 8% or less. The drying process of lumber requires that it be ventilated to allow interior moisture to migrate to the surface and evaporate. During the drying process lumber is typically stacked outdoors in what are commonly referred to as drying yards and left there over an extended period of time. Drying the lumber in this manner reduces its moisture content to approximately 22%. The lumber is then dried in a kiln until its water content is approximately 8%.
While lumber is being dried outdoors it is exposed to the elements causing it to darken in color and degrade in overall appearance. Direct sunlight and wind increases the dehydration rate of the wood which results in the exterior of the wood drying quickly which causes the outside wood cells to close. The closing of these wood cells seals the wood thus preventing interior moisture from escaping. This in turn creates surface cracks in the lumber which are commonly referred to as checking. To inhibit this some lumber manufacturers have draped burlap over the stacks of lumber. Burlap however retains moisture which promotes the growth of wood staining mold and mildew.
Manufacturers have also stored cut lumber in sheds for drying. These sheds have often been of totally enclosed construction which have proved to be costly in construction, maintenance and in properly controlling ventilation. Lumber has also been stored in open sheds which allow the lumber to be constantly ventilated. However, stacks of lumber located near the periphery of the shed are still exposed to the elements that cause checking such as sunlight, wind, and blowing rain and snow.
It thus is seen that a need remains for a method of inhibiting the checking of lumber as it dries in a more effective and cost efficient manner. Accordingly, it is to the provision of such a method that the present invention is primarily directed.